(1) Field of the Invention
This invention relates to a heating device, namely, a microwave oven for cooking foods or the like, in which electro-magnetic high frequency waves are used to rapidly cook foods.
(2) Description of the Prior Art
Many types of microwave ovens have been know as a domestic electric oven. But they have still a number of problems to be overcome. One of the problems is that parts of material to be heated are well-heated or over-heated, while other parts are not well-heated due to the microenergy distribution in a oven chamber.
Attempts have been made to reduce this problem with sitrrers, rotating antennas and other means. For example, in U.S. Pat. No. 3,851,133, there has been disclosed an antenna chamber which is disposed adjacent to the oven chamber and microwave energy is transferred thereto through radiation slots disposed in that side of the oven chamber adjacent the antenna chamber. In the antenna chamber, four arms of rotating antennas are provided.
However, as microwave radiation from the antenna chamber into the oven chamber is carried through a plurality of small slots, there result standing wave components since many slots form a type of a fixed arrayed antenna, and some part of microwave energy is lost in the antenna chamber.